Separation of hydrocarbons from water miscible liquids by distillation and washing



Nov. 26, 1946. W H,RUPP A 2,411,808

ET L SEPARATION OF HYDROCARBONS FROM WATER MISCIBLE LIQUIDS BYDISTILLATION AND WASHING Filed July 14, 1943 manufacture of many otherchemical 65% concentration at Patented Nov. 26, 1946 SEPARATION OF HYDROCARBONS FROM WATER MISCIBLE LIQUIDS BY DISTILLA- TION AND WASHINGWalter H. Rupp,

Wright,

Oil Development Company,

Delaware Application July 14,

8 Claims.

' not obtained when regenerating isobutylene from an acid solutionthereof.

Isobutylene has many important uses as a raw material in the manufactureof important commercial products, such as in the manufacture of butyleneto di-isobutylene and then hydrogenating the latter, in the manufactureof synthetic rubber of the butyl rubber type by copolymerizingisobutylene with a small proportion of a diolefin such as butadiene orisoprene, as well as in the products. However, for these various uses,the isobutylene should in most cases be relatively pure for bestresults, and a suitable process for obtaining it in desired purity hasbeen to contact mixed fluids (gaseous or liquid phase) containingisobutylene with a dilute sulfuric acid of, for instance, about ordinarytemperature and then to strip the resulting acid extract to 'liberatethe isobutylene. In this manner the stream which is stripped from theextract consists of isobutylene, in admixture with minor amounts, e. g.,about 2% to 6% or isobutylene polymers, such as (ll-isobutylene polymerswith traces of tri-isobutylene or higher polymers, about 30% or 40% ofalcohols, chiefly secondary and tertiary butyl alcohols, and water. Onepossible method for separating the isobutylene from these polymer andalcohol impurities is to fractionate the mix ture in a tower used as acombination scrubbing and iractionating tower in which the vapors richin isobutylene are fed in at the bottom of the tower and water is fed inat thetop of the tower for scrubbing the alcohols (which arewater-soluble) out from the rising vapors, with the result thatsubstantially pure isobutylene gas, having a purity of about 90% or 95%,is removed from the top of the tower while the bottoms from the towerconsists of a mixture of the scrubbing water, the alcohols, and thepolymers which have accumulated during the fractionation process. Thesebottoms also contain a small but substantial amount of isobutylene insolution, and heretofore, where any attempt has been made to recoverthis dissolved isobutylene, has been subjected to stripping by asuitable material, such a steam, this being done either in a separatetower or in a separate stripping section Mountainside, and Elizabeth, N.J., assignors' to Richard 0. Standard a corporation of 1943, Serial No.494,654 (Cl. 202-395) process of separating the entire bottoms streamdilute aqueous solution of the added on to the-lower part of andfractionating tower.

It has now been found that any isobutylene dissolved in the alcoholportion of the fractionating tower bottoms can be substantiallycompletely rejected from the alcohol phase'by diluting the alcohol phasewith water to about 242% alcohols. The polymer phase dissolvesisobutylene, however and is inherently immiscible with water or thealcohols, and therefore it is one object of the present invention toseparate and remove the alcohol-water solution from the bottoms beforestripping the latter with steam to recover dissolved isobutylene.Another object is to provide means especially adapted for effecting thisseparation and stripping isobutylene from the polymer in the mostefficient manner.

One advantage of this invention is that it permits the stripping oi thepolymer bottoms separarately from the much larger quantity ofalcoholwater solution, and thereby efiects the stripping with a muchsmaller quantity of eam than would be necessary to strip the entirefractionating tower bottoms. Another advantage which results from theone just mentioned is that if the stripping is effected in a sectionadded on to the bottom of the fractionating tower, this strippingsection may be constructed with a much smaller size. than if thealcohol-water solution were also being stripped. A still furtheradvantage is that the use or the smaller amount of steam for thisstripping permits a-relatively higher efiiciency in the fractionationand scrubbing taking place in the fractionating tower.

.The present invention comprises injection of the maximum volume ofdilution water into the top of thescrubbin the dilute alcohol-polymermixture into two separate liquid phases, one the upper lighter phaseconsisting essentially of oily polymer containing isobutylene gasdissolved therein, and the lower phase of dilute alcohol containingsubstantially no isobutylene or polymer. These phases may be separatedby gravity either by settling or by cenv trifuglng or by other suitablemeans, and this separation may be effected either in a settling drumentirely extraneous from the fractionating be carried out in a settlingsection added to the bottom of the iractionating tower. This separationis preferably carried out continuously and in conjunction with acontinuously operated scrubbing and fractionating tower. The polymerlayer only is sent to a. strippin section for removal of isobutylene.

the main scrubbing tower followed byseparating tain a temperature ofabout stripped from said polymer 501 molecular weight as by convertingthe dl-isobutling section integrally interpos In these several figures,like ed therebetween. reference numerals indicate like parts.

ing vapors and thereby remove the alcohols therefrom which arewater-soluble, and to dilute the alcohol so that a polymer layer willseparate. The desired temperatures are maintained isobutylene to removepolymers and alcohols therefrom,'to main- 100 to 150 F. in the bottom ofthe tower, about 100 to 130 F, in the middle portion and about 90 to 110F. at the top of the tower. Substantially pure isobutylene is ableisobutylene-regenerati shown, while the upper liquid phase consistingessentially of oily polymer-containing isobutylene dissolved therein isremoved from the settling drum 1 through line 9 and returned to theupper portion of the stripping section Ill constructed below andcommunicating with the fractionating tower 2. Steam is fed through lineI I into the lower portion of said strippingsection ID in order to stripthe dissolved isobutylene from the descending polymer solution. Theisobutylene ution rises out of the stripping section up through thebottom tray of the fractionating tower 2 and mixes with the other vaporsrising therethrough. Polymer liquid now substantially free fromdissolved isobutylene is removed from the stripping section III throughline II. The desired temperature may be maintained in this strippingsection III by suitable heating and/or cooling coils, not shown.

The equipment just described and illustrated in Fig. I is advantageouslyadapted to continuous ng apparatus not 4 e removal 01' the two liquid ngdrum 1 and removal of operation, and even th phases from the settli thor sub-atmospheric settling drum may hich-case it would,

remove a minor residual water phase.

Referring to Fig. II of th toms which coll fractionating to e drawing,ect in the bottom tray wer the bot- 5 of the flow by beneath andcommunicating with the fractionatmer' and isobutylene, ously throughline I6 and is removed continuwhile the polymer solution automatic withthe provision of a liquid level indicator control for regulating theflow of alcoholwater solution removed through line if If desired,instead, of using open stripping steam, one may use a reboiler, which,of course,

5 would be located in the same position as the stripping section II).

A conventional design of an isobutylene scrubber tower would require astripping section about 6 times the cross sectional area and about 10times the amount of stripping steam as for the system described above.This illustrates numerically the advantages of the invention in respectto the savings in steam consumption and in regard to the reduction insize of the stripping section required.

Although the in above as specificall isobutylene from t toms containingin its. broader as vention has been described y applied to the recoveryof he fractionating tower botpolymers, alcohols and water, pect, theinvention may be applied to any fractionating tower where the bottomsconsist of two or more immiscible liquids, and where the dissolved vaporoccurs primarily in solution in one of these liquids. Other ex- 7 amplesof applications of this invention are as follows: v

1. In a solvent extraction, for stripping extract from the liquidsolvent.

2. In manufacturing butadien butenes and butadiene from pol e, forremoving ymer lay-products.

V the alcohol-water phase and the dissolved isobutylene ous hydrocarbon1 alcohol manufacture, for removing isopropyl product.

It is not to the specific examples and have been given merely for tion'.

We claim:

1. In a process of intended that this invention be limited embodimentswhich the. sake of illustraseparating isobutylene in of alcohols, waterand polymer containing dissolved isobutylene by fracthe isobutylenevapor is removed overhead and the other materials in liquid form aremixed bottoms, the improvement comprising separating said mixed bottomsinto two immiscible liquids, a heavier one consisting essentially ofwater condissolved therein, suflicient water dilute the mixture to about2-12% alcohol strength, whereby isobutylene is rejected from thealcohol-water layer an lighter one consisting essentially ofpolymer-containing isobutylene dissolved therein, removing stripping thepoly-.

mer phase to remove therefrom.

2. Process according to claim 1; bottoms are miscible liquids tionationtakes place, and containing dissolved isobutylene vapor is stripped inthe lower part of the fractionating zone to recover isobutylene.

3. In a process of separating a tion of isobutylene vapor from a majorproporininor proportion of alcohols and polymers, by subjecting amixture of said compounds to fractionation and countercurrentisobutylene as vapor, and alcohols, polymers and as a mixture, theimprovement tion zone, passing the'.bottoms tionation zone by gravityinto a settling zone wherein gravity separation takes'placc, removing analcohol-water layer from the bottom of said settling zone, and passing apolymer layer convapor dissolved therein from theupper portion of saidsettling zone into a stripp dissolved isobutylene is removed from thepolymer layer, removing isobutylene-free polymer bottom ofsaid strippingzone, and recovering the isobutylene rreedby stripping.

4. In the process of separating a normally gaseirom a water-miscibleorganic water scrubbing, and removing improvement which comprisesadjusting the didthe ' mally gaseous lower part of the fractionationzone to reiect m immiscible organic liquid, pass "hydrocarbon liquidinto a stripping zone wherein lution of said water-miscible organicliquid with admixture to reject dissolved normally gaseous hydrocarbonsubstances therefrom, separating the hydrocarbon liquid from the dilutedwater-miscible organic liquid freed of the normally gaseous hydrocarbonthat has been rejected therefrom, then stripping the separatedhydrocarbon liquid to remove dissolved normally gaseous hydrocarbontherefrom, and recovering hydrocarbon from a uid mixed with 'a higheruid in a fractionation zone from which the mor hydrocarbon is removedoverhead base, the improvement which com introducing scrubbing waterinto an upper part of the fractionation zone, diluting the watermiscible organic liquid with said scrubbing water after the scrubbingwater has descended to a solved normally gaseous hydrocarbon from adwater-miscible organic liquid mixed with. the higher boilinghydrocarbonliquld, separating said hydrocarbon liquid from the dilutedwaterdissolved normally gaseous hydr stripped therefrom, and passing-normally gaseous hydrocarbon in gaseous phase from said stripping zoneup through the fractionation zone countercurrentiy to the scrubbingwater for removal overhead from the fractionation zone.

Process according to claim in which the liquid admixture is separated by6. hydrocarbon the diluted water-miscible organic gravity from liquidand the stripping .tion of the fractionating zone.

1. Process accord 5 in which the hydrocarbon liquid the dilutedwater-miscible organic liquid in-a zone outside the fractionation zone.

8. ss accor g to claim 5 in which the hydrocarbon liquid is separated bygravity from the diulted water-miscible organic liquid in a zonesuperimposed upon the stripping zone.

- WALTER H. RUPP.

RIOHARD O. WRIGHT.

zone is in a bottom poris separated by gravity from

